Horizontal earth boring drills utilizing manually operated transmissions connected to dual planetary final drives conventionally utilize automotive style clutch assemblies to enable the engagement and disengagement of the auger drive. This technology was borrowed from the automotive industry and is prevalent in many forms of construction equipment.
Such a system may consist of a driven steel clutch disk, lined with a suitable wear material, held against the flywheel of an internal combustion engine with a spring pressured plate. The driven disk is held firmly to the flywheel, until the spring exerted pressure is released. In the same way, an automobile is in gear, and remains so, until the clutch pedal is depressed, releasing the driven disk from the engine's flywheel.
This system has proven to be operable as a means for drive engagement and disengagement for gear driven horizontal boring machines. There exists a distinct disadvantage with the system, however, in the way that it relates to the operation of an earth drill.
A horizontal boring machine utilizes augers for excavation and removal of earth during the drilling process. The machine, through its drive train develops the necessary horsepower and torque requirements which will enable the drill string to penetrate, excavate and remove the earth for disposal. However, if the drill string encounters an obstruction that cannot be excavated, the energy that the machine developed to enable the excavation is transmitted back to the machine itself. The torque generated is unleashed at the machine, in that the machine physically tries to upset in a direction opposite to that of the applied torque. A comparison may be made to a hand drill that is being used to drill through a steel plate. If, for some reason, the drill bit hangs, the drill will experience the unloading of the torque energy, spinning away from the direction of the rotating drill bit. Since the clutch is manually operated, the machine operator must manually operate the clutch to avoid damage or injury. However, reaction time is often simply not sufficiently rapid to effect such manual actuation of the clutch in time to prevent injury or damage.
The prior art includes U.S. Pat. Nos. 1,857,897 and 3,037,576 which disclose control means associated with steering wheels. U.S. Pat. No. 4,230,200 illustrates a clutch which is disengaged upon release of a handle in a mower. U.S. Pat. No. 4,255,879 shows an auger with a dead man control.
Efforts to stop the engine of earth boring machines upon the development of torque as a result of the boring apparatus encountering an obstacle have produced unsatisfactory results because the engine has momentum built up which will not be released fast enough to avoid injury or damage.
Accordingly, it is an important object of this invention to provide apparatus for disconnecting the drive from the engine to the transmission gears as a result of the appearance of excessive torque in the hands of the operator so as to decrease or avoid the reaction time required to disconnect the drive.